The present invention generally relates to a branch joint box for performing branching of a circuit through branch joint of connectors of a wiring harness for a motor vehicle and more particularly, to prevention of penetration of water into the branch joint box.
In a branch joint box used for jointing a wiring harness for a motor vehicle to various electrical parts by branching, branch joint points are concentrated at one spot so as to reasonably and economically joint a circuit by branching. In response to rise of densities of wires of the wiring harness, various types of branch joint boxes have been developed.
FIGS. 1 and 2 show one example of known branch joint boxes. This known branch joint box includes a lower casing 1 and an upper casing 2. The upper casing 2 is fitted into the lower casing 1 so as to form a casing body 7. An upper side of the casing body 7, i.e., an upper portion of the lower casing 1 is closed by an upper cover 4, while a lower side of the casing body 7 is closed by a lower cover (not shown).
Since the branch joint box is provided in an engine room, etc. of the motor vehicle, countermeasures for preventing penetration of rainwater, etc. into the branch joint box and discharging the penetrated rainwater, etc. from the branch joint box are taken. As one of such countermeasures, a packing 3 is provided between an outer peripheral wall 1a of the lower casing 1 and the upper cover 4.
The lower casing 1 is made of synthetic resin and is formed by injecting synthetic resin into a cavity defined between an inner mold and an outer mold. However, in general, such a case may happen frequently at the time of molding of synthetic resin that the inner mold reaches a high temperature but the outer mold is of a relatively low temperature. By this temperature difference between the inner mold and the outer mold, the outer peripheral wall 1a of the molded lower casing 1 may warp inwardly as shown in FIG. 3 and as indicated by the two-dot chain lines in FIG. 4. If this warpage of the outer peripheral wall 1a of the lower casing 1 is produced, an upper portion of the outer peripheral wall 1a of the lower casing 1 is brought out of contact with the packing 3 as shown in FIG. 3 so as to form a gap therebetween and thus, rainwater, etc. may penetrate into the casing body 7 from this gap.
Therefore, conventionally, it has been necessary to take such a measure that molds are preliminarily manufactured in view of warpage of the outer peripheral wall 1a of the lower casing 1 or special molds leading to less warpage of the outer peripheral wall 1a of the lower casing 1 are employed, thereby resulting in rise of manufacturing cost of the molds. Meanwhile, if it is found that once molds for the lower casing 1 have been manufactured, the lower casing 1 molded by using the molds warps, the molds should be replaced by the above mentioned molds manufactured in view of warpage of the outer peripheral wall 1a of the lower casing 1 or the special molds leading to less warpage of the outer peripheral wall 1a of the lower casing 1, so that warpage of the outer peripheral wall 1a of the lower casing 1 cannot be corrected quickly.